Density functional theory (DFT) is applied to analyze ground and excited-state properties of some M(bpy)2L2 complexes (M = Ru, Os, L = CN, SCN, bpy = 2,2‘-bipyridine), both in the gas phase and in aqueous solution. In particular, vertical excitation energies were computed by the PBEO hybrid functional in the framework of a time dependent DFT (TDDFT) approach, whereas the polarizable continuum model (PCM) was used to take into account solvent effects. Our results in the gas phase show that the PBE0 functional provides accurate description of all the low lying electronic states considered and correctly reproduces the excitation spectra of such complexes. Some insights on the difference observed for these complexes in changing the central metal atom, the chemical environment, or the medium are given.

An atom-atom partitioning of the electrostatic energy between unperturbed molecules is proposed on the basis of the topology of the electron density. Atom-atom contributions to the electrostatic energy are computed exactly, i.e., via a novel six-dimensional integration over two atomic basins, and by means of the spherical tensor multipole expansion, up to total interaction rank L ) l A + l B + 1 ) 6. The convergence behavior of the topological multipole expansion is compared with that using distributed multipole analysis (DMA) multipole moments for a set of van der Waals complexes at the B3LYP/6-311+G(2d,p) level. Within the context of the Buckingham-Fowler model it is shown that the topological and DMA multipole moments converge to a very similar interaction energy and geometry (average absolute discrepancy of 1.3 kJ/mol and 1.3°, respectively) and are both in good to excellent agreement with supermolecule calculations.

In this paper, we present a detailed energetic decomposition of intramolecular O···X interactions (X being O, S, or a halogen atom) based on the interacting quantum atoms approach of Pendás and co-workers. The nature of these interactions (repulsive or attractive, more or less electrostatic) is discussed in the framework of Bader's atoms in molecules theory, a particular emphasis being put on delocalization (measured by delocalization indexes and in terms of the source function) and on the exchange contributions. Notably, the concept of exchange channels introduced by Pendás and collaborators provides means of rationalizing and predicting the presence of bond critical points, enhancing the physical meaning of bond paths.

In this article, we report a detailed study on halogen bonds in complexes of CHCBr, CHCCl, CH2CHBr, FBr, FCl, and ClBr with a set of Lewis bases (NH3, OH2, SH2, OCH2, OH(-), Br(-)). To obtain insight into the physical nature of these bonds, we extensively used Bader's Quantum Theory of Atoms-in-Molecules (QTAIM). With this aim, in addition to the examination of the bond critical points properties, we apply Pendás' Interacting Quantum Atoms (IQA) scheme, which enables rigorous and physical study of each interaction at work in the formation of the halogen-bonded complexes. In particular, the influence of primary and secondary interactions on the stability of the complexes is analyzed, and the roles of electrostatics and exchange are notably discussed and compared. Finally, relationships between QTAIM descriptors and binding energies are inspected.

The paper collects the answers of the authors to the following questions: Is the lack of precision in the definition of many chemical concepts one of the reasons for the coexistence of many partition schemes? Does the adoption of a given partition scheme imply a set of more precise definitions of the underlying chemical concepts? How can one use the results of a partition scheme to improve the clarity of definitions of concepts? Are partition schemes subject to scientific Darwinism? If so, what is the influence of a community's sociological pressure in the “natural selection” process? To what extent does/can/should investigated systems influence the choice of a particular partition scheme? Do we need more focused chemical validation of Energy Decomposition Analysis (EDA) methodology and descriptors/terms in general? Is there any interest in developing common benchmarks and test sets for cross‐validation of methods? Is it possible to contemplate a unified partition scheme (let us call it the “standard model” of partitioning), that is proper for all applications in chemistry, in the foreseeable future or even in principle? In the end, science is about experiments and the real world. Can one, therefore, use any experiment or experimental data be used to favor one partition scheme over another? © 2019 Wiley Periodicals, Inc.

Density functional theory and Bader's atoms-in-molecules theory share the same primary ingredient: the electron density, which is the fundamental physical observable in quantum chemistry. In this paper, we elaborate on the decomposition of the Kohn-Sham molecular energy in terms of Bader's partition, discussing how Pendás' Interacting Quantum Atoms framework could be adapted to a DFT context. Besides, another bridge between these two theories is built through a general formalism able to generate new local descriptors from any second-order density gradient expansion. These approaches are then applied to two classes of intramolecular bonds: between two electronegative atoms and intramolecular hydrogen bonds, illustrating how fruitful a dialog between both theories can be.

International audienceThe present work describes the first differentiation of enantiomers using the coupling of traveling wave ion mobility and mass spectrometry (TWIM-MS). This study was carried out on amino acids, the building blocks of proteins, which together with nucleotides, polysaccharides or lipids, are the main constituents of all living organisms. Herein, the enantiomers of aromatic amino acids (AA) such as phenylalanine, tryptophan and tyrosine are differentiated by TWIM-MS through their cationisation with copper(II) and multimer formation with D-proline (Pro) as a chiral reference compound. This methodology can be considered as an alternative approach to conventional methods for the separation of enantiomers. Moreover, quantification of the enantiomers can be performed easily and quickly using TWIM-MS analysis of the ionic complex [((D)Pro)(2)+(D/L)AA+Cu-II-H](+)

In this article, we assess the ability of various density functionals to predict accurate values for some basic properties of the bond critical points of about 50 small molecules, including the recently proposed reduced gradient variation rates and involving typical ionic and covalent bonds, agostic interactions, and van der Waals complexes. The relation between the computed deviations and the geometric variations are discussed, as well as the topology variations. The possible correlation of these descriptors to atomization energies is considered, and the relevance of an accurate QTAIM analysis for correct descriptions of potential energy surfaces is addressed. Finally, we provide typical margins of error for the evaluation of these quantities and discuss their consequences for computational applications.